Design, fabrication and characterization of an arrayable all-polymer microfluidic valve employing highly magnetic rare-earth composite polymer

We present a new magnetically actuated microfluidic valve that employs a highly magnetic composite polymer (M-CP) containing rare-earth hard-magnetic powder for its actuating element and for its valve seat. The M-CP offers much higher magnetization compared to the soft-magnetic, ferrite-based composite polymers typically used in microfluidic applications. Each valve consists of a permanently magnetized M-CP flap and valve seat mounted on a microfluidic channel system fabricated in poly(dimethylsiloxane) (PDMS). Each valve is actuated under a relatively small external magnetic field of 80 mT provided by a small permanent magnet mounted on a miniature linear actuator. The performance of the valve with different flap thicknesses is characterized. In addition, the effect of the magnetic valve seat on the valve's performance is also characterized. It is experimentally shown that a valve with a 2.3 mm flap thickness, actuated under an 80 mT magnetic field, is capable of completely blocking liquid flow at a flow rate of 1 ml min(-1) for pressures up to 9.65 kPa in microfluidic channels 200 mu m wide and 200 mu m deep. The valve can also be fabricated into an array for flow switching between multiple microfluidic channels under continuous flow conditions. The performance of arrays of valves for flow routing is demonstrated for flow rates up to 5 ml min(-1) with larger microfluidic channels of up to 1 mm wide and 500 mu m deep. The design of the valves is compatible with other commonly used polymeric microfluidic components, as well as other components that use the same novel permanently magnetic composite polymer, such as our previously reported cilia-based mixing devices.